Preparing stuff for paper making



to the stock to effect the precipitation.

.. and efliciency as alum fromv Patented Nov. 22, 1927. 1,650,022

UNITED STATES PATENT OFFICE.

ERNST MAHLER, OF NEENAII, AND HENRY A. ROTHCHILD', OF APPLETON, WISCONSIN, ASSIGNORS TO KIMBERLY-CLARK COMPANY, OF NEEN AH, WISCONSIN, A CORPORA- TION OF WISCONSIN.

PREPARING STUFF FOR PAPER MAKING.

in Drawing. Application filed September 21, 1923. Serial No. 664,075.

We have found that when such china clay is treated with the proper reagents and by the proper process the resulting alum and by-products incidental to the reaction may be added directly to the stuff without the necessity of separating or further refining the alum and without having to discard any of the said by-products. Furthermore, according to our process, the alum obtained is of the proper character for doing efliciently its full duty as a sizing reagent, while the by-products or waste materials incidental to the production of the alum also serve efiiciently as valuable ingredients of the stuff.

As illustrative of the manner in which our invention may be practically applied, the process as we have successfully used the same, may be carried out in the following manner.

Example: 750 lbs. of ch na clay, 450 lbs. of water and 750 lbs. of sulphuric acid Baum (77.6%) are thoroughly mixed and incorporated and are then charged into an Our invention relates to improvements in preparing stufi' for paper making, and has particular reference to the manner in which certain of the sizing. and loading ingredients are prepared and added to the paper stock or stuff before the latter goes to the paper making machine.

Specifically our invention is of particular importance when applied to a paper making process in which alum is employed for fixing or precipitating the size upon the fibers of the paper making stock, such step in the preparation of the stuff being conveniently effected in the beater or other receptacle in which the stock is mixed before it is conducted to the wire.

Heretofore the usual: practice has been to' add the size, for example, rosin soap, to the Stuff and after thoroughly incorporating same with the fiber, a suitable proportion of alum, usually of the basic variety is added So far as We are aware the preparing and supplying of such alum to the paper maker as been done with sole reference to its use a precipitant in the sizing process and without reference to any other ingredients which may be added to the fiber for loadin or otherwise influencing 'the character 0% the finished paper.

The principal object of our invention is to provide a process, or a treatment step, whereby the alum desired to be added to the stock for sizing purposes may be prepared on the spot, as needed, from one of the ingredients, for example, china clay, which may be added to the paper stuff-for loading or other purposes. Other objects of our invention are to provide an improved step in the art of paper stock preparation, and to provide an improved process for producing china clay.

In carrying out our invention, we take advantage of the fact that china clay, which is a desirable and in certain cases a necessary loading ingredient for certain classes of paper, when of the proper purity suitable for paper making, is as to its chemical compost tion practically pure hydrated aluminum silicat A certain proportion of such china clay ingredient is used for preparing the desired amount of basic alum to be added to the stock.

vided with a suitable stirring arrangement. The mixture is then heated by steam until the temperature of the mass reaches approximately 170 C. or that corresponding ['0 a steam pressure of pounds per square inch. During the application of heat the mass is stirred sufliciently to distribute the material which is of the consistency of a paste but has a certain degree of fluidity. The principal object of adding water is to prevent caking and to insure ease in stirring with proper distribution. However, only sufiicient water to effect such purpose is used because we find that the reaction is more rapid with the highly concentrated acid.

Although no catalyzer or other reagent need be employed,-we find that with a steam pressure of 100 pounds per square web a batch as above indicated may be completely treated in approximately 1 hour and 30 minutes. For the sake of speed and economy it is advisable to keep the temperature above C. Upon calculating the theoretical quantities needed for the reaction according to the chemical formula therefor, it will be observed that we use a considerable excess of china clay. This insures the production of an alum of the basic type such as is desirordinary digester of suitable capacity proterial containing such our improved process is able for paper making, rather than an ordinary um.

After the reaction is completed the mixture contains,- in addition to water which carries in solution the desired basic alum, a few percent. of deh drated aluminum silicate and a considera le percentage of silica in extremely finely divided form. Such mixture, after being diluted and screened, is discharged directly into the beater or other receptacle in which the paper stuff or stock is mixed or sized. The alum in the solution does its full duty in fixing the size on the fibers of the stufl while the silica, aluminum silicate and any other ingredients resulting from the original composition of the china clay go into the paper as filling material.

This mixture or solution will obviously contain a considerable percentage of silica due to the reaction. The addition of maa large percentage oi silica which is not ordinarily considered as desirable or valuable filling ingredient might be considered objectionable. However, we find that silica in the particular form produced by this reaction is not at all undesirable as a filler and furthermore upon calculation of the proportion of such silica present in the final paper, it will be found that the percentage is so minute that it could have no noticeable afiect upon the finished paper. At any rate, the paper produced by fully equal to that to the old method when produced according ordinary alum is added to the stock.

The described details of the process being illustrative merely of one phase of our incontinued long enough to form vention, the scope of same should be determined b reference to the appended claims, said claims being construed as broadly as possible, consistent with the state of the art.

We claim:

1. The improvement in the art of paper making which consists in treating clay with sulphuric acid to form alum and adding a solution of said alum to the stuff together with a by-product of the reaction.

2. The improvement in the art ofstufi preparation for paper making which consists in treating a silicate of aluminum with sulphuric acid in the presence of water to form a mixture of an alum solution and a by-product of the reaction and adding said mixture directly to the stuff.

3. The improvement in the art of preparing stufli' for paper making which consists in treating china clay with sulphuric acid in the presence of water and at a tempera ture in excess of 100 0., the reaction being a basic alum solution and subsequently discharging the said solution and the by-products of the treatment into the stufi.

4. The improvement in the art of paper making which consists in digesting china clay with sulphuric acid in presence of sufiicientwater to'facilitate stirring of the mass and to prevent caking, heatin the mixture} at a temperature above 100 for a suflicient length of time to produce a solution of basic alum and subsequently adding the contents of the digester to the stufi.

ERNST MAHLER. HENRY A. ROTHCHILD. 

